When using a crossbow in the offhand position, it will not load fireworks whether from inventory or from the hotbar, even if you are only carrying fireworks instead of fireworks and arrows.
Offhand crossbow will still load regular arrows regardless.
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We're tracking this issue as MC-159075, so this ticket is being resolved and linked as a duplicate.
That ticket has already been resolved as working as intended, which means this is not considered a bug and won't be fixed. Please do not leave a comment on the linked ticket.
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